RSIs are utilized for remotely collecting data in the field and communicating the collected data to one or more centralized locations. For example, RSIs are utilized in tracking and/or monitoring assets that are stored and/or transported in association with wireless transceivers, such as radio frequency identification tags (RFIDs). In such implementations, such as those described in U.S. Patent Application Publication No. 2005/0093702 A1, an RSI has sometimes been previously referred to as a “wireless reader tag” or “WRT.” The data regarding the tracked and/or monitored assets is communicated by an RSI to one or more central servers for processing. Such data is useful, for instance, in supply chain management. Such data further is useful, for instance, in homeland security, especially when the assets being tracked and/or monitored are being imported into the United States from foreign countries.
Of course, the RSIs of the present invention are preferably capable of wireless communications with external devices. For example, the RSI preferably communicates with other RSIs in forming one or more wireless networks. Furthermore, the RSI preferably communicates with a gateway that itself serves as a bridge to other networks, such as the Internet, a cellular network, or a Satellite network.
In order to reduce power consumption by the RSIs, attempts have been made to utilize a “wake-up receiver” to determine, according to predetermined criteria, when a higher power radio should be turned on for two-way wireless communications with the gateway. Such a wake-up sequence was described in the aforementioned U.S. Patent Application Publication No. 2005/0093702 A1. In that reference or other references, the wake-up receiver may have been referred to as a “WT Component,” or on occasion, as a “tag turn-on circuit” or “TTOC.” In addition, the signal received by the wake-up receiver for waking up the RSI is transmitted by a wake-up transmitter. The wake-up transmitter occasionally has been referred to as a “tag turn-on” or “TTO” in this previous reference or another reference, and the wake-up transmitter is capable of sending signals to other RSIs and/or gateways that may include wake-up receivers, TTOCs, or the like, for wake-up of the other RSIs and/or gateways. Unfortunately, the wake-up sequence performed in the aforementioned reference does provide a sufficient amount of reduction in the power consumption of the RSI or RSI-equivalent. Further, the previous wake-up sequence does not provide the opportunity for different functions to be triggered at different power levels.
The present invention relates in particular to a stepped wake-up sequence of an RSI in activating circuits thereof in response to a wake-up signal that is received from a gateway or another RSI. The stepped wake-up sequence provides extended duration of the life of the battery power supply of the RSI, especially in a noisy radio frequency (RF) environment. This wake-up sequence and the preferred circuit diagrams for performing this wake-up sequence is deemed to be an improvement over the general wake-up sequence performed by the “WT Component” described in detail, for example, in incorporated International Patent Application Publication No. WO 03/098851 A1.